Abstract

We report the fabrication and testing of a 10 GHz grid amplifier utilizing sixteen GaAs chips each
containing an HBT differential pair plus integral bias/feedback resistors. The overall amplifier consists of
a 4x4 array of unit cells on an RT Duroid™ board having a relative permittivity of 2.2. Each unit cell
consists of an emitter-coupled differential pair at the center, an input antenna which extends horizontally
in both directions from the two base leads, an output antenna which extends vertically in both directions
from the two collector leads, and high inductance bias lines. In operation, the active grid array is placed
between a pair of crossed polarizers. The horizontally polarized input wave passes through the input
polarizer and couples to the input leads. An amplified current then flows on the vertical leads, which
radiate a vertically polarized amplified signal through the output polarizer. The polarizers serve dual
functions, providing both input-output isolation as well as independent impedance matching for the input
and output ports. The grid thus functions essentially as a free-space beam amplifier. Calculations indicate
that output powers of several watts per square centimeter of grid area should be attainable with optimized
structures.